1. Field of the Invention
The present invention relates generally to a container, and more particularly to a thermoplastic container provided with a decorative label. This container is, in particular, a container with a neck intended to contain a product to be dispensed, the label serving to identify the product or its properties, and/or to indicate the directions for use of the product. This container may be used in the fields of cosmetics, agricultural food products, dermatology, household or paint products.
More particularly, the container is a bottle, a tube-type bottle, or a tube, whose body includes one or several non-developable surfaces. Usually, containers of this kind are obtained by the extrusion or injection of a parison at a temperature higher than the fusion temperature of the material constituting it and by blow molding the parison in an appropriate mold.
2. Discussion of the Background
In conventional methods, it is easy to fix a decorative label on containers with a developable surface having a cylindrical shape by straightforward glueing, for example by using a self-adhesive label made of paper which has been previously decorated in its flat state. This labeling adds a step to the construction of the container, and as a result it complicates the manufacture of the container.
About twenty years ago, a combined method was developed for blow molding a bottle with simultaneous labeling. This involves depositing a parison and a label made of paper or a plastic material in an appropriate openable mold and positioned opposite one another. This method is known under the name of "IML" (In-Mold Labeling). After the parison has been blow-molded, and before it has been taken out of the mold, the label is welded onto an external surface of the final container. This combined method is an improvement compared to glueing the label after removal from the mold, since the decorated container can be obtained in a single step. Another advantage is that the label can be made of a plastic material that virtually does not deteriorate. Because of this, during use of the product introduced into the container, the label can be neither spoiled nor detached as a result of the action of humidity or of product residues flowing over the label due to oversight on the part of the user. Moreover, this method makes it possible to obtain a unit with a perfectly smooth surface, in particular in the transition zones between the edges of the label and the body of the container. In other words, the label is "embedded" in the wall of the container.
However, the IML process has the major drawback that it is only applicable to the decoration of containers with developable surfaces. Indeed, when one is concerned with a container whose body includes a non-developable surface with a complex curvature, for example concave and convex zones, neither the depositing of a self-adhesive label, nor the application of the IML process are possible with the labels that are currently used, without the forming of creases in the label, without tearing the label, and/or without forming of unsightly air bubbles between the external surface of the container and the label. This effect is even more of a nuisance when the label is in part transparent.
To improve the attachment of the label and to prevent the formation of air bubbles between the surface of a bottle with a non-developable surface and the label, it is envisaged in WO-A-88 08361 to obtain asperities in the mold intended to allow air to escape between the label and the external surface of the bottle. Low pressure or suction is applied at the same time. This process has, on the one hand, a drawback that it is complicated and expensive, and on the other hand, the disadvantage that it produces a bottle with little aesthetic appeal because of the asperities that are visible on the label.
Moreover, DE-A-1 604 577 discloses a plastic label having air evacuation means intended to be fixed onto a blow-molded plastic container. These means are obtained in the form of perforations or striations. The containers to be provided by this prior document have a developable surface. The fusion temperature of the material of the label is equal to, or less than, the fusion temperature of the material constituting the container. In these conditions, an application of the label onto a non-developable surface of a container is not possible without deterioration of the label during the thermoforming of the finished container.